Device for applying thin films to articles

ABSTRACT

The cathode sputtered by ion bombardment and the anode have a common axis of symmetry in the vacuumized gas-discharge chamber. The anode is formed by two tubes of the same outside diameter. These tubes are installed along the axis of symmetry with a gap between the ends, said gap allowing the passage of the sputtered material of the cathode onto the article installed in the gap. The gas-discharge chamber is located in a magnetic field whose lines of force coincide in direction with the axis of symmetry. This magnetic field is intended to produce a low-pressure discharge in the chamber.

April l7, 1073 E. M. BARKHUDAROV T L 3,128,246

DEVICE FOR APPLYING THI NQPILMS TO ARTICLES Filed Aug. 25, 1971 VIII/1,...

United States Patent 3,728,246 DEVICE FOR APPLYING THIN FILMS T0 ARTICLES Eduard Mikhailovich Barkhudarov, ulitsa Chonkadze a, kv. 27; Nikolai Arsenovich Kervalishvili, prospekt Chavchavadze 19, kv. 16; and Vladimir Parmenovich Kortkhondzhia, nlitsa Dzerzhinskogo 4, all of Tbilisi, U.S.S.R.

Filed Aug. 25, 1971, Ser. No. 174,765

Claims priority, application U.S.S.R., Jan. 22, 1970,

Int. Cl. C23c /00 US. Cl. 204-498 2 Claims ABSTRACT OF THE DISCLOSURE The cathode sputtered by ion bombardment and the anode have a common axis of symmetry in the vacuumized gas-discharge chamber. The anode is formed by two tubes of the same outside diameter. These tubes are installed along the axis of symmetry with a gap between the ends, said gap allowing the passage of the sputtered material of the cathode onto the article installed in the gap. The gas-discharge chamber is located in a magnetic field whose lines of force coincide in direction with the axis of symmetry. This magnetic field is intended to produce a low-pressure discharge in the chamber.

The present invention relates to improvement of the devices for applying thin films by the cathode sputtering method and can be used in various branches of electronics, for example in manufacturing resistors, capacitors, superconducting wire, etc., as well as in microelectronics for the production of microcircuits.

Widely known in the art is a device for applying thin films comprising a vacuumized chamber containing a sputtering appliance. The latter is made in the form of a gas discharge chamber whose walls function as a cathode. The anode is located inside the chamber, coaxially with the cathode. The gas-discharge chamber is located in a longitudinal magnetic field. The anode is arranged along the longitudinal axis of the magnetic field and is constituted by a bar in which case the cathode is usually cylindrical in shape and made of a material which is sputtered by ion bombardment.

The article to be coated with a thin film is placed into the gas-discharge chamber, in the gap between the cathode and anode. Under the eifect of ion bombardment the material of the cathode is sputtered and the flux of sputtered material is deposited on the article.

Inasmuch as the article is located in the zone of the discharge (which takes place, as already stated, between the anode and cathode) the spray-coating conditions are impaired. As a rule, the spray-coating devices are used for simultaneous treatment of a group of articles secured to a carrying element. This element, introduced into the zone of discharge, further worsens the conditions of spray coating.

Besides, it must be borne in mind that part of the flux sputtered from the cathode is totally lost since it goes past the article.

Finally, for producing a homogeneous coating of a cylindrical article the latter has to be rotated around its axis which complicates considerably the design of the device as a whole.

In some cases the article is secured directly to the anode. In this case the discharge can be used only under high pressure conditions (above 10- torr) since under the low-pressure conditions the fastening of the article to the anode results in perturbation of the accelerating anolyte layer of electrons. All this, taken together, tells 3,728,246 Patented Apr. 17, 1973 on the quality of the applied film because of the presence of neutral particles of residual gas in the flux.

An object of the present invention is to provide a device for applying thin films wherein the article would be located in such a manner as not to interfere with the spray-coating conditions and with the discharge, which would produce a homogeneous coating of a cylinder without rotating it, and would provide conditions for a more efiicient utilization of the flux of the sputtered material.

This object is accomplished by providing a device for applying thin films to articles wherein, according to the invention, the anode of the gas discharge chamber is formed by two hollow tubes arranged along an axis of symmetry and having the same outside diameter, the tubes being installed with a gap between the ends, this gap serving to pass the sputtered material of the cathode onto the portion of the article located between said tubes.

In such a design of the device the article is located outside the zone of the high-voltage discharge and does not, therefore, influence its quality. In handling cylindrical articles, the flux is applied to their surfaces uniformly from all sides which dispenses with the necessity of rotating the article. Finally, this design ensures the most complete utilization of the flux of the sputtered material.

It is practicable that the sputtered part of the cathode should be made in the form of a surface described by rotating a parabola whose focus coincides with the center of the gap.

This will provide optimum conditions for the utilization of the flux of the sputtered material. .2:

Now the invention will be described in detail by way of example with reference to the accompanying drawing which illustrates the device for applying thin films to articles.

Arranged in consecutive order in the vacuumized chamber 1 are a heater 2 for cleaning the article of volatile oxides, means 3 of ionic cleaning (e.g., Penning cell) with an anode 4 and a cathode 5 having an opening in the center for the passage of the article 6, and a gas discharge chamber 7 in which the material is sputtered on the article. This chamber is, in fact, an ionic sputtering appliance.

The gas discharge chamber 7 contains an anode 8 installed along the longitudinal axis of symmetry of this chamber, and a cathode consisting of electrodes 9 and 10 subjected to the same potentials.

The electrodes 10 are constituted by the walls of the chamber 7, are located symmetrically to its longitudinal axis of symmetry and are made of a material with which the article must be coated The anode 8 installed inside the cathode consists of two hollow tubes located along said axis of symmetry with a gap between their ends. In a general case the electrode 10 may have any shape, for example a round straight cylinder. To improve the quality of the applied film and intensity the flux of the sputtered material applied to the article, the cross section of the electrode 10 is a parabola whose focus coincides with the center of the gap between the tubes which make the anode 8.

The article 6 is transferred from one treatment position to another by continuous-motion mechanisms 11.

Installed outside the vacuumized chamber 1 is a solenoid 12 which builds up the longitudinal magnetic field in the gas discharge chamber 7, and the ionic cleaning appliance 3 in which case the tubes making up the anode 8 should follow the shape of the magnetic field or, in other words, they must not intersect the magnetic lines of force of this field. For a uniform magnetic field the tubes have the shape of round straight cylinders and said axis of symmetry must be parallel to the lines of force of the magnetic field built up by the solenoid 12.

The claimed device uses the through-flowing inert gas, say, argon at a pressure of from to 10' 10- mm. Hg.

The device functions as follows:

The article 6 enters the heater 2 and is heated there to a temperature required for degassing. Then the continuousmotion mechanism 11 introduces the article into the ionic cleaning appliance 3 where, if necessary, the surface of the basis metal is cleaned of heat-resistant oxide films or is subjected to ionic pickling. After cleaning, the article enters the gas-discharge chamber 7 where a low pressure high-voltage discharge is produced with an anodic layer whose thickness depends on the strength of the magnetic field of the solenoid 12. The produced ionic current bombards the electrode 10, thus sputtering it.

The value of the ionic current depends on the gas pressure, anode area, discharge voltage and magnetic field strength.

The article 6 is inserted through the space of the tubes of the anode 8 and is set between their ends.

The ions accelerated in the anodic layer of the gas discharge bombard and sputter the electrode 10 of the cathode. Part of the sputtered atoms gets into the gap between the anode tubes and settles on the surface of the basis metal, forming a thin film. Thus, the article is outside the zone of the gas discharge during spray-coating; hence it does not influence the discharge conditions.

To produce multilayer films, a number of consecutive gas-discharge chambers can be used, each chamber containing an electrode 10 of a different material.

Using the claimed device, the applied films may range in thickness from 10 A. to microns.

What is claimed is:

1. A device for applying thin films to articles comprising a vacuumized chamber with a sputtered cathode and anode which have a common axis of symmetry, said anode being formed by two tubes of the same outside diameter located inside the cathode along said axis of symmetry with a gap between the tube ends through which the sputtered material of said cathode can pass onto the portion of said article located between said tubes, a means for creating a magnetic field in which the gas discharge chamber is placed in such a manner that said axis of symmetry coincides with the direction of the lines of force of said magnetic field which is intended to produce a lowpressure discharge in the gas-discharge chamber.

2. A device according to claim 1 wherein the sputtered portion of the cathode is a surface produced by revolving a parabola around said axis of symmetry, the focus of said parabola coinciding with the center of the gap.

References Cited UNITED STATES PATENTS 2,146,025 2/1939 Penning 204-2 98 3,616,400 10/1971 Wasa 204298 3,616,450 10/1971 Clark 204298 JOHN H. MACK, Primary Examiner S. S. KANTER, Assistant Examiner 

